In what context does ble_nus_data_handler execute?

[la-ble]

I'm trying to understand whether my callback assigned to the data_handler variable during initialization of the Nordic UART Service gets executed in an interrupt or somewhere 'less serious'. Basically, I'm wondering if I'm going to perform a long operation, whether I should instead queue the message to process later in the main loop.

Also, are we guaranteed to receive the entire 20B message all at once or might bytes trickle in randomly? For example, if I begin each message with a type byte, can I assume that the first byte I receive in this callback is always the 0th byte (my type) of the message?

S110 v8.0.0 soft device API documentation doesn't seem to offer much more to answer these questions.

[Stefan Birnir Sverrisson]

Hi

The softdevice callbacks have ARM interrupt priority 3, which is same as NRF_APP_PRIORITY_LOW. When your code executes in the NUS handler it blocks other callbacks. It is a good practice to execute long code in the main context instead. More on priorities (1) (2)

The transfer is always raw hexadecimal bytes and they should be received in the same order as they are sent.